Science Fair Project Encyclopedia
Sand is an example of a class of materials called granular matter. Sand is a naturally occurring, finely divided rock, comprising particles or granules ranging in size from 0.063 to 2 mm. An individual particle in this range size is termed a sand grain. The next smaller size class in geology is silt: particles below 0.063 mm down to 0.004 mm in size. The next larger size class above sand is gravel, with particles ranging up to 64 mm (see grain size for standards in use).
The most common constituent of sand in inland continental settings and non-tropical coastal settings, is silica (silicon dioxide), often in the form of quartz, because of the considerable hardness of this mineral. However, the composition of sand varies according to local rock sources and conditions. Arkose is a sand or sandstone with considerable feldspar content which is derived from the weathering and erosion of a usually nearby granite. Much of the fine white sand found in coral reef settings is ground-up limestone of biological origin. Some locations have sands that contain magnetite, chlorite, glauconite, or gypsum. Sands rich in magnetite are dark to black in color, as are sands derived from basalt. The chlorite-glauconite bearing sands are typically green in color, as are sands derived from basalts (lavas) with a high olivine content. The gypsum sand dunes of the White Sands National Monument in New Mexico are famous for their bright, white color. Sand deposits in some areas contain garnets and other resistant minerals, including some small gemstones.
The study of sand is called arenology
Uses of sand
Sand is often a principal component of the aggregate used in the preparation of concrete. Sand manufactured at rock crusher plants for use as an aggregate is called mansand. Graded sand is used as an abrasive in sandblasting and is also used in media filters for filtering water.
Hazards of sand
Bags of sand now typically carry labels warning the user to wear respiratory protection and avoid breathing the fine silica dust. There have been a number of lawsuits in recent years where workers have sought damages after they developed silicosis, a lung disease caused by inhalation of fine silica particles.
People have been severely injured and even killed after digging sand "caves" in large dunes or sandhills when the cave collapsed upon them.
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